Analysis of hydrocarbon under-filled Miocene deep-water reservoirs, eastern Mexico offshore




Apango Perez, Fernando Agustin

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Hydrocarbon exploration in the deep-water portion of the southwestern Gulf of Mexico commenced a decade ago, but discoveries have not been able to meet the optimistic expectations based on historical success in the northern Gulf of Mexico. Based on the existence of organic-rich source rocks and high-quality Miocene reservoir rocks, this research initially hypothesized that the lack of significant hydrocarbon accumulations in some prominent traps in the northern Catemaco fold belt (Veracruz Trough) is the result of an ineffective sealing and/or trapping mechanism. By integrating well core, 3D seismic, and other well data provided by the Mexican National Hydrocarbon Commission, this thesis attempts to determine the cause of hydrocarbon under-filled or dry Miocene traps within the Veracruz Trough using the structures drilled by Pemex-operated Kunah-1 and Yoka-1 wells as case studies. Three hypotheses are considered and analyzed: top seal leakage, the existence of unmapped shallow spill points, and late trap formation relative to the timing of hydrocarbon charge. Seal bed leakage analyses, which involved pressure data analysis and MICP laboratory measurements on cuttings, suggest that the evaluated intra reservoir and top seal rocks are at least moderately effective. In addition, 3D seismic structural interpretation around the Yoka-1 trap strongly suggests that the spill points are much deeper than fluid contacts. However, the trap formation assessment showed that by the time the traps began to develop, the oil generation phase was exhausted and gas generation was at a very late stage for the most prominent source rocks. Consequently, a more robust explanation for the Kunah-1 and Yoka-1 under-filled structures is poor timing between the generation and migration of hydrocarbons and trap volume evolution. A high-level economic assessment was made to determine if it would be commercially viable to produce some of the natural gas reserves that have already been found in the Catemaco fold belt. A notional gas development that would tie in production from the Kunah, Lakach, and Piklis fields into an onshore gas processing plant, was proposed and analyzed. The net present value calculated for this project suggests that the high costs of building the required infrastructure and the relatively low forecasted future prices of natural gas, make the profitability of a deep-water gas development project around the study area unlikely at the present time


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